Manufacturing zinc oxide



Aug. 28, 19434. c. R. BERINGER MANUFACTURING ZINC OXIDEl Filed May 24:, 1929 ZL/venan' IMW Patented Aug. I28, 1934 tres eas , QFFEC MANUFACTURING ziNo oxmE Application May 24, 1929, Serial No. 365,727 In Hungary May 29, 1928 1A Claim. (o1. ca -14s) My invention relates to an improved process for manufacturing zinc oxide or zinc white.

In my `prior patents, for instance in my Hunr garian Patent No. 88,995, or in my Austrian Patv`l entNo. 105,794, `Ihave shown that zinc oxide may of very good quality, this being due to the fact Athat heating of the bath is `no longer effected Vfrom beneath, as in prior processes, but exclusively from above, thereby avoiding the fierce bubbling of the bath which usually takes place and causes impurities to go over `and mix with the vapor emanating from the' bath. `A further 1 advantage of my said process consists in that that I make use of the heat of the reaction to carry on the process whereby a considerable saving of fuel is attained.` I

The object of mypresend invention is to yimprove my previously mentioned process and to providea new' process which will result in a still further 'saving of fuel and which will enable the adjustment of the process at will, such ad justment offering the -advantage that, on the one hand, the quality ofV the zinc white produced may be altered in accordance with the varying requirements of the market, etc., and that, on

the other hand, the same quality of zinc White may be manufactured from materials containing a different percentage of zinc.

The main feature of my present invention is that, during manufacture, the reverberatory furnace is revolved, continuously or intermittently, around an axis parallel or approximately parallel .to the direction of the current of oxidizing gases `and vapors iiovfingthrough the said furnace, whereby the entire circumferential Wall of the said reverberatory furnace gradually assumes a position beneath the bath. Accordingly, in my new process the heat of reaction is utilized not only to keep the bath molten but also to keep the bottom surface of the bed'of the furnace at the required temperature. Thereby the advantage is attained that the process may become fully self- 'sustaining in regard to the heat of reaction, the latter being usually suilicient alone to make the reaction continuous if and after the process is once started by means of anauxiliary heating. A further advantage of my new process is that the chamotte lining of the revoluble cylinder con- `emanating from the bath b thereby produced is stituting the reverberatory furnace, by being brought continually beneath the bath and then being again lifted above the bath, not only heats the said bath by giving up some part of its own heat to the said bath but is itself cooled to a certain extent simultaneously which resultsrin a longer life of the said lining.

The improved method, therefore, for producing zinc white from metallic zinc or metals containing zinc consists-in melting the metal in a rotating drum by external heat, passing an oxidizing gas axially of the drum above the surface of the pool and at a height sufficiently spaced therefrom to provide an intervening zinc vapor zone for oxidizing the zinc vapors; the external heat is then materially reduced While the current o-f gas is continuous, the oxidized vapors beingcollected beyond the drum.

My invention will be readily understood from the following description taken in connection with the accompanying drawing in which Figure l is a vertical longitudinal section showing an appara-V tus constructed according to my invention, the section being taken on line 1-1 in Figure 2; and Figure 2 is a vertical cross section taken on line 80 2-2 in Figure 1.` l

In the drawing, c indicates the heating chamber or appliance furnishing the external heat necessary to start the process, u designates the reverberatory furnace, and g designates the flue for drawing olf the burnt zinc vapor.

The heating chamber c, as shown, constitutes an ordinary re place provided with bars for 'i supporting the fuel; butit is to be understood that instead of the said firing place fire appliances` or burners of any other kind, for instance oil or gas burners or electrical heating, may also be used for the said starting purpose.

The reverberatory furnace a comprises a cylinder supported by means of rollers lc.V Any kind of mechanism may be provided for rotating the said cylinder continuously or intermittently. `The mechanism shown consists of intermeshing toothed gears r1 and r2, the latter connected to an electric motor n by means of a Worm T5 and wormwheel r3. The motor n may be regulated in regard to its number of revolutions and it may be reversed in a manner by means (not shown) well known to those skilled in the art.

To start the action, the zinc or metals bearing zinc and zinc alloys brought into the furnace a for instance through an opening h is first melted by means of the products of combustion furnished by the combustion chamber c, and the zinc vapor then oxidized in the furnace by means of the air entering the said furnace at the opening d, the said opening having its bottom surface d1 at a level above the top surface of the bath b so that the oxidizing gas does not contact the upper surface of the liquid bath directly but flows above the layer of the zinc vapors which are continuously emanating from the said bath and are burning to ZnO from above thereby constantly separating the liquid bath from the said stream of air or other oxidizing gas. The zinc vapors having been oxidized in the furnace pass through the opening f into the flue g *andv thence into a collecting plant, etc., (not shown on the drawing) the said plants being of any known or suitable" kind.

Once the oxidation of the zinc vapors has started, the firing may be, partly or wholly, stopped, the heat obtained by the reaction being usually sufficient to keep the metal molten and' to ensure the continuity of the surface volatilization of the zinc. The air necessary for the burning of the zinc vapors may enter, for example, by natural draft or otherwise, at the opening m left between the furnace cylinder a and the firing appliance c or through special openings made in the firebox (not shown),

During the burning of the zinc vapors the furnace cylinder a is continually or intermittently revolved, whereby the entire circumferential wall of the furnace is continuously or gradually brought beneath the bath b, so that the said bath is kept at the required temperature by the heat of reaction itself which, owing to the revolving movement of the furnace, compensates the loss of heat due to the absence of a separate external firing acting upon the bottom of the said furnace.

The process may be also carried into effect by revolving the furnace cylinder intermittently at times only, when the lining of the furnace has attained such a temperature as to render it expedient to be brought into position beneath the bath b.

The quality of the product can be easily ad- Vjusted by means of changing or regulating the speed of the revolving movement performed by the reverberatory furnace. An increase in speed of revolution causes an increase in the speed of volatilization, whereas a decrease in the speed of revolution causes a decrease in the speed of volatilization. An increase in the speed of volatilization results in a larger part of the impurities contained in the bath being carried away withy the zinc vapor, so that in case of purposely manufacturing a product of somewhat inferior quality, the furnace cylinder a is revolved faster, thereby reducing the costs of manufacture owing to the fact that losses of heat are thereby reduced and the product is formed more quickly. For similar reasons, with raw materials containing more impurities, the cylinder a has to be revolved slower, and with purer raw material it has to be revolved faster in order to obtain in both cases a product of approximately equal quality.

The impurities present in the bath b, chiefly lead, settle gradually in the bottom of the bath, and for the purpose of collecting the said impurities an annular excavation p is formed within the cylinder a where the material more or less saturated with impurities can be ladled out from time to time through the opening h provided in the bottom part of the ue g or through openings (not shown) provided in the excavation p.

The reverberatory furnace shown consists of a single revoluble cylinder; but it is, however, obvious that several cylinders may be arranged in series. The axis of the cylinder or cylinders is arranged horizontally, as shown. The air current may be supplied by an exhaust plant (not shown) and the revolving movement of the cylinder may be effected by simply oscillating the cylinder a instead of revolving it around its own longitudinal axis.

Results attained with my new process, if properly carried out have shown the following:-

l. Fuel required in the heating appliance only is but 5- to 10% in weight of the zinc oxide produced.

2. Two men per shift are suiicient for a production of 5 tons daily, and

3. Power required is. only l5 H. P. for a daily production of 5 tons.

What I claim is:-

A method of producing zinc White from metallic zinc or metals containing zinc, which consists in melting the metal in a rotatable horizontally disposed drum under conditions to establish a pool of molten metal in said drum, passing any oxidizing gas axially of said drum abovey the surface of the pool at a height suffiu ciently spaced therefrom to provide an intervening zinc vapor zone, to oxidize the zinc vapors, materially reducing the external heating while continuing the current of said gas, and rotating the drum at a predetermined speed, and collecting the oxidized vapors beyond the drum.

CORNELIUS RAYMOND BERINGER. 

